This invention relates generally to a method for integrating an image sensor with optical components, and more particularly to a wafer level integrating method for bonding un-sliced wafers having image sensors, wafer-sized substrates and optical components thereon.
With the advent of the multimedia age and rapid development of the 3C (computer, communication and consumer) industries, there is an increasing demand for various electro-optical devices utilizing image sensors, such as digital cameras, digital video devices, and scanners. An image sensor is used to convert an optical image focused on the sensor into electronic signals. The image sensor typically includes an array of light detecting elements for producing a signal corresponding to the intensity of light impinging on the element so as to be used to display a corresponding image on a monitor or to provide information about the optical image.
The image sensors are generally classified into two categories, i.e. CCD (charge coupled device) image sensors and CMOS (complementary metal oxide semiconductor) image sensors. CCD image sensors have been developed over 30 years and much earlier than CMOS image sensors. Currently, most electro-optical devices use CCD image sensors, primarily due to their mature fabrication techniques and applications. However, CMOS image sensors have undergone rapid development in the recent years because they can integrate the peripheral controlling circuits so as to reduce the complexity and size of the electro-optical devices as well as the electric power consumption.
FIG. 1 is an exploded sectional view of a conventional image-sensing device 100. The image-sensing device 100 comprises a image sensor 110, a color filter 120 and a transparent plate 130. The image sensor 110 includes a two-dimensional array of light sensor cells, such as CCD or CMOS. The color filter 120, such as a trichroic filter, including R, G and B color filters (122, 124 and 126) is provided at the light-incident side of the image sensor 110. The transparent plate 130, for example, formed of glass is provided at the light-incident side of the color filter 120.
FIG. 2 is a schematic drawing of a prior art packaged image sensor. The bonding and packaging procedures of an image-sensing device are as follows. First, an image sensor 200 is bonded to a carrier 210, wire bonds 220 are electrically connected between the image sensor 200 and the carrier 210 and outside electrical leads 230 are connected to the terminals of the carrier 210. The image sensor 200 are precision optically aligned to the color filter 240 by using targets lithographically reproduced on both the image sensor 200 and the color filter 240. An optical coupling composition 250 is uniformly spread on the top of the image sensor 200. The color filter 240 is positioned over the image sensor 200 and disposed onto it so that the optical coupling composition 250 can be uniformly spread beneath the color filter 240. The color filter 240 and the image sensor 200 are optically aligned with each other by way of alignment targets, and then the image sensor 200/color filter 240 assembly is checked for debris or bubble entrapment. A conventional UV curable adhesive at each end of the color filter 240 is used for stacking the color filter 240 in place. Lastly, a transparent plate 260 is bonded onto the carrier 210 to protect the assembly from contaminants of foreign particles and moisture.
The conventional bonding and packaging procedures of the image sensor are based on a single die; that is, each die must be diced from a semiconductor wafer for further bonding and packaging processes. Since all bonding and packaging processes are based on chip scale, the precision requirement is very important and the procedure is very complicated. Moreover, the above-mentioned processes of bonding and packaging should be implemented in a very clean environment since foreign matter and moisture present within the space 270 will degrade the sensing quality. Therefore, manufacturing an image sensor through the conventional processes is subject to several disadvantages, for example, complex and heavy processes, low product yield, long manufacture cycling time and significant cost.
Accordingly, the present invention provides a wafer level integrating method for bonding un-sliced wafers having image sensors and a wafer-sized substrate including optical components thereon, comprising the steps of: bonding a wafer-sized substrate including the optical components thereon to a zeroth order light reflective substrate through an adhesive to form a composite substrate; and bonding the composite substrate to an un-sliced wafer including image sensors thereon to form a resultant wafer for further packaging processes.
Additional advantages, objects and features of the present invention will become more apparent from the description which follows.